Scanning acoustic microscopes, which operate at ultra-high frequencies (250-1000 MHz), permit the visualization of tissues on a microscopic scale similar to that provided by light microscopy, with the added benefit that the tissue sample does not need to be biopsied. Potential clinical applications of acoustic microscopy include in situ imaging of cells on the skin, in the esophagus, in the reproductive tract, and in arteries. There is a great clinical need to develop an acoustic microscope that can be mounted on the tip of a cardiac catheter, gastroscope, colonscope, bronchoscope, or laparoscope. We propose an innovative high speed, 200 MHz, scanning acoustic microscope for in situ imaging that is based on a linear array of zinc oxide (ZnO) ultrasonic transducers. The ZnO transducer array will be fabricated using reactive sputtering. ZnO films deposited by reactive sputtering will result in structures with the appropriate dimensions for in situ use and will result in extremely uniform arrays that can be easily and inexpensively manufactured using standard photolithography techniques. Our clinical collaborator has found that a 200 MHz operating frequency provides an optimal tradeoff between the required resolution for imaging cells and depth of penetration of the ultrasound. PROPOSED COMMERCIAL APPLICATION The proposed miniature scanning acoustic microscope will enable high resolution, in situ tissue characterization that will dramatically reduce the cost and time associated with diagnosing numerous medical aliments that currently require tissue biopsies and pathological examination.